Thanks Josep for your help. I am regulating temperature which is slow.My task (Regulation) is part of Main task (see p1). Is the average cycle time as shown on Task configuration - Monitor (see p2) that I have to put for the PID_fixcycle?

Thanks againPape

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Due to I also have digital inputs, I keep this task (at 4000us) for them and put a new one only dedicated to temperature regulation at (100ms) but the output of the PID was very slow. I use ziegler & Nichols method to have Kp, Tn and Tv=0. I tried to increase this cycle time but facing overshooting. How to solve that? Can someone have a look using teamviewer to help?

thanksPape

Last edited by Pape on Thu Apr 20, 2017 8:46 am, edited 1 time in total.

My output card varies from 0 to 65534 (16bit).On CTRL_PID I set LL=0, LH=100 and use LIN_TRAFO to scale it.

Results: I have noise all time from temp sensor that make the output fluctuating. I used SUP=0.5 but not big change. I also put LH=10000, the noise is reduced a lot but controller output is very slow in this case.

First of all. I d try to work with SI units. For example: anOut at 12000 means 100V over the resistance. Working in PID with V and °C independices your system from the converters used.

Sup is not a filter is a dead band and only works when the error is nearest to 0. Previous at PID use a LowPass filter in feedback. As your system response is slow A cut frequency of 10Hz would have to work. If your feedback has noise after this filter you have somethibg wrong reading temperature.

I would work with ft_pid. It has anti wind up in integral.

One more question: When you calculate G for Ziegler Nichols you have used temperature(in digital counts)/Volts or Amps (in digital counts)?.

It finally works. I had error on my input scaling. That's why your instructions didn't work the first time.The lowpass filter solved the noise. I am using 4-20mA. With Ziegler Nichols I use the temp (C) or the WORD but in percent. (G=%delta temp/ %delta CV ) in manual mode.

look the results attached

thanks againPape

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